Bounds on a Kaluza-Klein excitation of the ${{\mathit Z}}~$boson or photon in $\mathit d$=1 extra dimension. These bounds can also be interpreted as a lower bound on 1/$\mathit R$, the size of the extra dimension. Unless otherwise stated, bounds assume all fermions live on a single brane and all gauge fields occupy the 4+$\mathit d$-dimensional bulk. See also the section on “Extra Dimensions” in the “Searches” Listings in this $\mathit Review$.

VALUE (TeV) CL% DOCUMENT ID TECN  COMMENT • • We do not use the following data for averages, fits, limits, etc. • • $>4.7$ 1 MUECK 2002 RVUE Electroweak $>3.3$ 95 2 CORNET 2000 RVUE ${{\mathit e}}{{\mathit \nu}}{{\mathit q}}{{\mathit q}^{\,'}}$ $>5000$ 3 DELGADO 2000 RVUE $\epsilon _{{{\mathit K}}}$ $>2.6$ 95 4 DELGADO 2000 RVUE Electroweak $>3.3$ 95 5 RIZZO 2000 RVUE Electroweak $>2.9$ 95 6 MARCIANO 1999 RVUE Electroweak $>2.5$ 95 7 MASIP 1999 RVUE Electroweak $>1.6$ 90 8 NATH 1999 RVUE Electroweak $>3.4$ 95 9 STRUMIA 1999 RVUE Electroweak 1  MUECK 2002 limit is 2$\sigma $ and is from global electroweak fit ignoring correlations among observables. Higgs is assumed to be confined on the brane and its mass is fixed. For scenarios of bulk Higgs, of brane-SU(2)$_{\mathit L}$, bulk-U(1)$_{\mathit Y}$, and of bulk-SU(2)$_{\mathit L}$, brane-U(1)$_{\mathit Y}$, the corresponding limits are $>4.6$ TeV, $>4.3$ TeV and $>3.0$ TeV, respectively. 2  Bound is derived from limits on ${{\mathit e}}{{\mathit \nu}}{{\mathit q}}{{\mathit q}^{\,'}}$ contact interaction, using data from HERA and the Tevatron. 3  Bound holds only if first two generations of quarks lives on separate branes. If quark mixing is not complex, then bound lowers to 400$~$TeV from $\Delta {\mathit m}_{{{\mathit K}}}$. 4  See Figs.$~$1 and 2 of DELGADO 2000 for several model variations. Special boundary conditions can be found which permit KK states down to 950$~$GeV and that agree with the measurement of $\mathit Q_{{{\mathit W}}}$(Cs). Quoted bound assumes all Higgs bosons confined to brane; placing one Higgs doublet in the bulk lowers bound to $2.3~$TeV. 5  Bound is derived from global electroweak analysis assuming the Higgs field is trapped on the matter brane. If the Higgs propagates in the bulk, the bound increases to $3.8~$TeV. 6  Bound is derived from global electroweak analysis but considering only presence of the KK ${{\mathit W}}$ bosons. 7  Global electroweak analysis used to obtain bound independent of position of Higgs on brane or in bulk. 8  Bounds from effect of KK states on $\mathit G_{\mathit F}$, $\alpha $, $\mathit M_{{{\mathit W}}}$, and $\mathit M_{{{\mathit Z}}}$. Hard cutoff at string scale determined using gauge coupling unification. Limits for $\mathit d$=2,3,4 rise to $3.5$, $5.7$, and $7.8$ TeV. 9  Bound obtained for Higgs confined to the matter brane with ${\mathit m}_{{{\mathit H}}}$=500 GeV. For Higgs in the bulk, the bound increases to $3.5~$TeV.

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